Unipolar or bipolar chopping converter with two magnetically coupled windings

ABSTRACT

In order to reduce the cost of a chopping converter supplying a continuous voltage at the terminals of a load (Z), a circuit with two windings (Lp, Ls) and a single magnetic core is proposed, according to the present invention, which enables the cost and the size of the circuit to be reduced. It is then necessary to add two diodes (D 3,  D 4 ) to the circuit, but these elements are inexpensive and of small size.

TECHNICAL FIELD

The invention relates to a unipolar or bipolar chopping converter,operating in the quadrants (Is>0; Vs>0) and (Is<0; Vs<0), and with zerooutput current or voltage, having magnetically coupled windings, whichmay be configured with the regulation mode adapted in current source orvoltage source. It applies to all types of terrestrial, naval or aerialequipment using this type of chopping converter, particularly theelectromechanical actuator controls of regulating automatons for turbineengines.

STATE OF THE PRIOR ART

The control of electrical actuators with an RL type load (resistor andinductance in series) may be achieved either by application of aregulated voltage at the terminals of the control coil of the actuator,or by a current source, this latter solution often being preferred insevere environments essentially because it enables the power used tocontrol the accessory to be limited.

Chopping current sources may conventionally be grouped together amongcurrent sources using the inductance of the load as energy storageelement during the chopping operation, with as consequence theapplication at the terminals of the load, at the chopping frequency, ofan alternatively positive and negative voltage, the transitions betweenthese two states ideally being considered as instantaneous, and currentsources supplying a continuous current and, consequently, a continuousvoltage at the terminals of the load, in which the energy storageelement for the chopping is situated on the control card itself.

Chopping current sources using the inductance of the load as energystorage element have the advantage of having a control that is, at firstsight, simple. They comprise few or possibly no inductive elements,which leads to a certain saving in the dimensions of the circuit. On theother hand, they have a certain number of disadvantages. They have ahigh dependency vis-à-vis the value of the inductance of the load: thecapability of controlling the instantaneous current in the switches ofthe current source depends directly on the charge inductance value. Theresistance to short circuits between the output terminals of theconverter or between any output terminal and earth is very difficult.Indeed, in the event of short circuit of the load, it is not possible,except by adding components, to limit the instantaneous current.Consequently, in practice it is necessary to add an inductance at theoutput of the converter in order to limit the short circuit current, toadd a protection and very rapid cut off device to limit the maximumvalue of the short circuit current, to add a circuit for demagnetisingthe output inductance to manage the cut off after the detection of theshort circuit at the output, to over-dimension the interfaces (inputfiltering capacitor) so that they can withstand the short circuitcurrent. Concerning the electromagnetic compatibility aspect (conductedemissions essentially), these converters are difficult to rendercompatible with aeronautic emission standards, if a high choppingfrequency is desired to limit the size of the passive components of theconverters, especially if the load is controlled at the end of severalmetres of cable. The result is a chopping frequency reduced typically tobelow 10 kHz and an obligation to dimension an output filter (sharedmode and differential mode) that will play a prominent role in thestability of the assembly and will have a non negligible size. This typeof chopping current source is restricted to high power applications, forwhich a low chopping frequency is not necessarily a handicap.

For converters supplying a continuous voltage at the terminals of theload, the chopping no longer takes place in the load but the current (orthe voltage) is regulated at the output of a chopping convertercomprising an inductance storing at least all of the energy transferredto the load and a capacitor is added to smooth out the output voltage.Consequently, the output voltage is virtually continuous at theterminals of the load. There is therefore less difficulty in meetingaeronautic standards for noise emitted in conduction. In the event ofshort circuit of the load, the current in the converter remainsnaturally limited. Chopping frequencies exceeding 100 kHz may beenvisaged, limited in fact by the efficiency of the converter and theperformance of the gate control circuits of switch elements.

FIG. 1 a is an electrical diagram of a converter of the prior artsupplying a continuous voltage at the terminals of a load. The circuitis supplied by a positive voltage Vp (for example +25V) and a negativevoltage Vm (for example −25V) with respect to earth. Il comprises twoelements T1 and T2 each comprising two windings magnetically coupledaround a magnetic core. The windings of a same element T1 or T2 arewound in opposition as indicated by a point in FIG. 1 a. The winding E1of the element T1 has a first end connected to the voltage Vp throughthe intermediary of a diode D5 inversely mounted in relation to thevoltage Vp, its second end being to earth. The winding E2 of the elementT1 has a first end connected to a first terminal of a switch Q3 in whichthe second terminal is connected to the voltage Vp. The second end ofthe winding E2 is connected to the output terminal S1P of the circuit.The winding E3 of the element T2 has a first end connected to thevoltage Vm through the intermediary of a diode D6 inversely mounted inrelation to the voltage Vm, its second end being to earth. The windingE4 of the element T2 has a first end connected to a first terminal of aswitch Q4 in which the second terminal is connected to the voltage Vm.The second end of the winding E4 is connected to the output terminal S1Pof the circuit. A smoothing capacitor C1 is connected between the outputS1P and the earth.

The converter is transformed into current source by the addition ofmeans of measuring the output current, a suitable regulation andmodulator. This is shown in FIG. 1 b where the load connected to theoutput of the converter is represented in the form of a resistor Rc andan inductance Lc connected in series. The output current is measured bya measuring means 1 that delivers a representative signal to a firstinput of a regulation means (or equaliser) 2. A second input Ec of theregulation means 2 receives a set point signal. The output signal of theregulation means 2 is addressed to the input of a modulator 3 thatdelivers a command signal SQ3 to the switch Q3 and a command signal SQ4to the switch Q4.

The converter illustrated in FIG. 1 a comprises therefore four windingsand two magnetic cores, which leads to a relatively high cost and arelatively large size of the circuit.

DESCRIPTION OF THE INVENTION

In order to reduce the cost and the size of a chopping convertersupplying a continuous positive, negative or zero voltage at theterminals of a load, a circuit with two windings coupled on a singlemagnetic core is proposed, according to the present invention. It isthen necessary to add two diodes to the circuit, but these elements areof low cost and of low size.

A first subject of the invention consists in a chopping convertersupplied by a positive voltage and a negative voltage with respect toearth, and delivering an output voltage between a first output terminaland a second output terminal, comprising two windings wound inopposition around a magnetic core, the number of turns of the secondwinding being greater than the number of turns of the first winding, thefirst end of the first winding being connected to a mid point of a firstbranch connecting the positive voltage to the negative voltage andcomprising a first diode and a second diode inversely mounted, the midpoint of the first branch being situated between the first diode and thesecond diode, the second end of the first winding being connected toearth, the first end of the second winding being connected to a midpoint of a second branch connecting the positive voltage to the negativevoltage, the part of the second branch connecting its mid point to thepositive voltage comprising, arranged in series, a first switch formingmeans and a third diode directly mounted in relation to the positivevoltage and together forming a unidirectional switch with direct andinverse blocking capability, the part of the second branch connectingits mid point to the negative voltage comprising, arranged in series, asecond switch forming means and a fourth diode directly mounted inrelation to the negative voltage and together forming a unidirectionalswitch with direct and inverse blocking capability, the second end ofthe second winding being connected to the output terminal.

Advantageously, a smoothing capacitor is connected between the firstoutput terminal of the converter and earth.

Also advantageously, in the second branch connecting the positivevoltage to the negative voltage, said arrangement in series consists inarranging the first and second switch forming means on the side of therespective positive or negative voltages and arranging the third andfourth diodes on the side of the mid point of the second branch.

The switch forming means may be chosen among MOS transistors, bipolartransistors and IGBT transistors or any other switch having abidirectional conduction capability and a direct blocking capability.

The converter may further comprise a means of measuring the outputvoltage of the converter, said measuring means delivering an outputsignal representative of the output voltage to a first input of aregulation means in which a second input receives a set point signal,the regulation means delivering a signal supplied to the input of amodulator in which a first output sends a command signal to the firstswitch forming means and in which a second output sends a command signalto the second switch forming means, the converter being therebyconfigured in voltage source.

The converter may further comprise a means of measuring the outputcurrent (is) of the converter, said measuring means delivering an outputsignal representative of the output current of the converter to a firstinput of a regulation means in which a second input receives a set pointsignal, the regulation means delivering a signal supplied to the inputof a modulator in which a first output sends a command signal to thefirst switch forming means and in which a second output sends a commandsignal to the second switch forming means, the converter beingconfigured in current source.

The chopping converter according to the invention may equip anelectromechanical actuator control, a regulating automaton, a turbineengine or terrestrial, naval or aeronautic equipment.

The chopping converter according to the present invention may operateaccording to the following methods.

A first method comprises the following steps, for an operating cycle andto pass a negative current in the load:

a first step during which a first switch forming means are open, thefourth diode is conducting, the second switch forming means are closedand the first, second and third diodes are blocked during a first partof the cycle, the converter operating in continuous mode or indiscontinuous mode,

a second step, following the first step, during which, the first andsecond switch forming means are open, the second diode is conducting andthe first, third and fourth diodes are blocked during a second part ofthe cycle, this second part of the cycle not ending the cycle if theconverter operates in discontinuous mode and ending the cycle if theconverter operates in continuous mode,

-   -   a third step, following the second step if the converter        operates in discontinuous mode, during which the first and        second switch forming means are open and the first, second,        third and fourth diodes are blocked during a third part of the        cycle ending at the end of the cycle.

A second method comprises the following steps, for an operating cycleand to pass a positive current in the load:

a first step during which a first switch forming means are closed, thethird diode is conducting, the second switch forming means are open andthe first, second and fourth diodes are blocked during a first part ofthe cycle, the converter operating in continuous mode or indiscontinuous mode,

a second step, following the first step, during which the first diode isconducting, the first and second switch forming means are open and thesecond, third and fourth diodes are blocked during a second part of thecycle, this second part of the cycle not ending the cycle if theconverter operates in discontinuous mode and ending the cycle if theconverter operates in continuous mode,

a third step, following the second step if the converter operates indiscontinuous mode, during which the first and second switch formingmeans are open, the first, second, third and fourth diodes are blocked,during a third part of the cycle ending at the end of the cycle.

A third method comprises the following steps, for an operating cycle andto pass a negative current in the load, the converter operating incontinuous mode:

a first step during which a first switch forming means are closed, thethird diode is conducting, the second switch forming means are open andthe first and fourth diodes are blocked, the second diode being blockedif the voltage at the first output with respect to earth is, in absolutevalue, sufficiently low, during a first part of the cycle,

a second step, following the first step, during which the first diode isconducting, the first and second switch forming means are open and thesecond, third and fourth diodes are blocked during a second part of thecycle,

a third step, following the second step, during which the second switchforming means are closed, the fourth diode is conducting, a first switchforming means are open and the first, second and third diodes areblocked, during a third part of the cycle,

a fourth step, following the third step, during which the second diodeis conducting, the first and second switch forming means are open andthe first, third and fourth diodes are blocked, during a fourth part ofthe cycle ending at the end of the cycle.

A fourth method comprises the following steps, for an operating cycleand to pass a positive current in the load, the converter operating incontinuous mode:

a first step during which a first switch forming means are closed, thethird diode is conducting, the second switch forming means are open andthe first, second and fourth diodes are blocked during a first part ofthe cycle,

a second step, following the first step, during which the first diode isconducting, the first and second switch forming means are open and thesecond, third and fourth diodes are blocked during a second part of thecycle,

a third step, following the second step, during which the second switchforming means are closed, the fourth diode is conducting, a first switchforming means are open and the second and third diodes are blocked, thefirst diode is blocked if the voltage at the first output with respectto earth is, in absolute value, sufficiently low, during a third part ofthe cycle,

a fourth step, following the third step, during which the second diodeis conducting, the first and second switch forming means are open andthe first, third and fourth diodes are blocked, during a fourth part ofthe cycle ending at the end of the cycle.

BRIEF DESCRIPTION OF DRAWINGS

The present invention may best be understood and other advantages andparticularities will become apparent by reference to the followingdescription, provided as an indication only and in no way limiting andby referring to the accompanying drawings in which:

FIG. 1 a is an electrical diagram of a chopping converter of the priorart supplying a continuous voltage at the terminals of a load,

FIG. 1 b is an electrical diagram of the converter of FIG. 1 a used aschopping current source by addition of means of measuring the outputcurrent, as well as suitable equaliser and modulator,

FIG. 2 is an electrical diagram of a chopping converter supplying acontinuous voltage at the terminals of a load and that has led to thedevelopment of the present invention,

FIG. 3 is an electrical diagram of a chopping converter supplying acontinuous voltage at the terminals of a load, according to theinvention,

FIGS. 4A to 4N illustrate the operating mode of the present invention,

FIGS. 5A to 5F are chronograms corresponding to different operatingmodes illustrated by FIGS. 4A to 4N,

FIG. 6 a shows the principle of using the converter according to theinvention as voltage source,

FIG. 6 b shows the principle of using the converter according to theinvention as current source.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

FIG. 2 is an electrical diagram of a chopping converter supplying acontinuous voltage at the terminals of a load, and that has led to thedevelopment of the present invention. This converter may be, in the sameway as for the converter described in FIGS. 1 a and 1 b, converted intochopping current source by the addition of a means (direct or indirect)of measuring the current of the load and suitable equaliser andmodulator. As for FIG. 1 a, the circuit is supplied by a positivevoltage Vp (for example +25V) and a negative voltage Vm (for example−25V) with respect to earth. It comprises a transformer forming elementand comprising three windings Lp, Ls1 and Ls2 wound around a uniquemagnetic core. The winding direction is indicated by a point in FIG. 2.The windings Ls1 and Ls2 are mounted in series to constitute thesecondary of the transformer forming element, their shared point (theirfirst ends) being to earth. The winding Lp constitutes the primary ofthe transformer forming element. The second end of the winding Ls1 isconnected to the voltage Vp through the intermediary of a diode D1inversely mounted in relation to the voltage Vp. The second end of thewinding Ls2 is connected to the voltage Vm through the intermediary of adiode D2 inversely mounted in relation to the voltage Vm. The winding Lphas a first end connected to the cathode of a diode D3 and to the anodeof a diode D4. The second end of the winding Lp is connected to theoutput terminal SP of the circuit. A first terminal of a switch Q1 isconnected to the anode of the diode D3 and its second terminal isconnected to the voltage Vp. A first terminal of a switch Q2 isconnected to the cathode of the diode D4 and its second terminal isconnected to the voltage Vm. A smoothing capacitor Cs is connectedbetween the output SP and earth. The output SM may be connected tomechanical earth directly, or via a resistor, depending on the needs ofthe user.

The switches Q1 and Q2 are advantageously N-channel or P-channel MOSFETtransistor elements, depending on the needs of the user. They may bereplaced by any other switch having a bi-directional conductioncapability and a direct blocking capability.

Np being the number of turns of the winding Lp, Ns1 being the number ofturns of the winding Ls1 and Ns2 being the number of turns of thewinding Ls2, Np is greater than Ns1 and Ns2, for example Ns1=Ns2=0.75Np.

FIG. 2 mentions the following voltages:

vq1 at the terminals of Q1,

vq2 at the terminals of Q2,

vd1 at the terminals of D1,

vd2 at the terminals of D2,

vd3 at the terminals of D3,

vd4 at the terminals of D4,

vls1 at the terminals of Ls1,

vls2 at the terminals of Ls2,

vlp at the terminals of Lp, and

vs at the terminals of Cs, i.e. the output voltage of the converter.

FIG. 2 also mentions the following currents:

ils1 flowing through the winding Ls1,

ils2 flowing through the winding Ls2,

ilp flowing through the winding Lp, and

is flowing through the load Z of the converter, i.e. the output current.

The current source of FIG. 2 has a certain advantage compared to thecurrent source of the prior art illustrated in FIG. 1 a. A reading ofmeasurements carried out on an assembly such as shown in FIG. 2 has madeit possible to observe that, in an unexpected manner, the anode of thediode D1 and the cathode of the diode D2 were always at the samepotential. These two points have therefore been electrically connectedand one of the secondary windings has been deleted. This is shown inFIG. 3 where the remaining secondary winding is known as Ls, its numberof turns is such that Ns is less than the number of turns Np of theprimary winding Lp. FIG. 3 shows a load Z connected at the output of theconverter.

The operation of the chopping converter will now be explained inreference to FIGS. 4A to 4N as a function of the commands (closing,opening) sent to the switches Q1 and Q2. In these figures, the currentsthat flow in the circuit are indicated by bold lines. As will be seen,the converter according to the invention is a two quadrant converter:

(vs>0, is>0) and (vs<0, is<0).

FIGS. 4A to 4F concern an operating mode where a single transistor Q1 orQ2 (forming switch) conducts when the output current is positive (is>0)or when the output current is negative (is<0).

FIGS. 4A to 4C concern an operating mode where the output current “is”is negative, for an operating cycle (from t=0 to t=T).

FIG. 4A illustrates a first step of the operating cycle between theinstants t=0 and t=t₁ (where t₁<T). The circuit may operate incontinuous mode and in discontinuous mode. During this step, the commandof the circuit is such that:

Q2 and D4 conduct,

Q1, D1, D2 and D3 are blocked.

FIG. 4B illustrates a second step of the operating cycle, between theinstants t=t₁ and t=t₂. The circuit may operate in continuous mode (inthis case t₂=T) or in discontinuous mode. During this step, the commandof the circuit is such that:

D2 conducts,

Q1, Q2, D1, D3 and D4 are blocked.

FIG. 4C illustrates a third step of the operating cycle, uniquely forthe discontinuous mode, between t=t₂ and t=T. During this step, thecommand of the circuit is such that:

Q1, Q2, D1, D2, D3 and D4 are blocked,

the current “is” flowing in the load is supplied by the energyaccumulated in the capacitor Cs.

FIG. 5A shows the chronograms corresponding to the operating modeillustrated by FIGS. 4A to 4C for a discontinuous mode, therefore for anoperating cycle comprising three steps.

FIG. 5B shows the chronograms corresponding to the operating modeillustrated by FIGS. 4A and 4B for a continuous mode, therefore anoperating cycle comprising two steps.

FIGS. 4D to 4F concern an operating mode where the output current “is”is positive, for an operating cycle (from t=0 to t=T).

FIG. 4D illustrates a first step of the operating cycle between theinstants t=0 and t=t₁ (where t₁<T). The circuit may operate incontinuous mode and in discontinuous mode. During this step, the commandof the circuit is such that:

Q1 and D3 conduct,

Q2, D1, D2 and D4 are blocked.

FIG. 4E illustrates a second step of the operating cycle, between theinstants t=t₁ and t=t₂. The circuit may operate in continuous mode (inthis case t₂=T) or in discontinuous mode. During this step, the commandof the circuit is such that:

D1 conducts,

Q1, Q2, D2, D3 and D4 are blocked.

FIG. 4F illustrates a third step of the operating cycle, uniquely forthe discontinuous mode, between t=t₂ and t=T. During this step, thecommand of the circuit is such that:

Q1, Q2, D1, D2, D3 and D4 are blocked,

the current “is” flowing in the load is supplied by the energyaccumulated in the capacitor Cs.

FIG. 5C shows the chronograms corresponding to the operating modeillustrated by FIGS. 4D to 4F for a discontinuous mode, therefore for anoperating cycle comprising three steps.

FIG. 5D shows the chronograms corresponding to the operating modeillustrated by FIGS. 4D and 4E for a continuous mode, therefore for anoperating cycle comprising two steps.

FIGS. 4G to 4N concern an operating mode where the two transistors Q1and Q2 (forming switch) conduct when the output current is negative(is<0) and when the output current is positive (is>0). The operationdescribed is in continuous mode.

FIGS. 4G to 4J concern an operating mode where the output current “is”is negative, for an operating cycle (from t=0 to t=T).

FIG. 4G illustrates a first step of the operating cycle, between theinstants t=0 and t=t₁. During this step, the control of the circuit issuch that:

Q1 and D3 conduct,

Q2, D1 and D4 are blocked,

D2 is blocked if the voltage in output SP with respect to earth is, inabsolute value, sufficiently low.

FIG. 4H illustrates a second step of the operating cycle, between theinstants t=t₁ and t=t₂. During this step, the command of the circuit issuch that:

D1 conducts,

Q1, Q2, D2, D3 and D4 are blocked.

FIG. 4I illustrates a third step of the operating cycle, between theinstants t=t₂ and t=t₃. During this step, the command of the circuit issuch that:

Q2 and D4 conduct,

Q1, D1, D2 and D3 are blocked.

FIG. 4J illustrates a fourth step of the operating cycle, between theinstants t=t₃ and t=T. During this step, the command of the circuit issuch that:

D2 conducts,

Q1, Q2, D1, D3 and D4 are blocked.

FIGS. 4K to 4N concern an operating mode where the output current “is”is positive, for an operating cycle (from t=0 to t=T).

FIG. 4K illustrates a first step of the operating cycle, between theinstants t=0 and t=t₁. During this step, the command of the circuit issuch that:

Q1 and D3 conduct,

Q2, D1, D2 and D4 are blocked.

FIG. 4L illustrates a second step of the operating cycle, between theinstants t=t₁ and t=t₂. During this step, the command of the circuit issuch that:

D1 conducts,

Q1, Q2, D2, D3 and D4 are blocked.

FIG. 4M illustrates a third step of the operating cycle, between theinstants t=t₂ and t=t₃. During this step, the command of the circuit issuch that:

Q2 and D4 conduct

Q1, D2 and D3 are blocked,

D1 is blocked if the voltage in output SP with respect to earth is, inabsolute value, sufficiently low.

FIG. 4N illustrates a fourth step of the operating cycle, between theinstants t=t₃ and t=T. During this step, the command of the circuit issuch that

D2 conducts,

Q1, Q2, D1, D3 and D4 are blocked.

FIG. 5E shows the chronograms corresponding to the operating modeillustrated by FIGS. 4G to 4J, therefore for an operating cyclecomprising four steps.

FIG. 5F shows the chronograms corresponding to the operating modeillustrated by FIGS. 4K to 4N, therefore for an operating cycle alsocomprising four steps.

FIG. 6 a shows the principle of using the converter according to theinvention as voltage source by the addition of means 11 of measuring thedifferential voltage between the outputs SP and SM, a suitable equaliser12 receiving a set point Ec and a suitable modulator 13. The outputs ofthe modulator 13 supply the command voltages SQ1 and SQ2 of thetransistors Q1 and Q2.

FIG. 6 b shows the principle of using the converter according to theinvention as current source by the addition of means 21 of measuring“is” output currents of the converter, a suitable equaliser 22 receivinga set point Ec and a suitable modulator 23. The outputs of the modulator23 supply the command voltages SQ1 and SQ2 of the transistors Q1 and Q2.

1. Chopping converter supplied by a positive voltage (Vp) and a negativevoltage (Vm) with respect to earth, and delivering an output voltagebetween a first output terminal (SP) and a second output terminal (SM),the latter terminal being connected directly to earth or through aresistor, comprising two windings (Ls, Lp) wound in opposition around amagnetic core, the number of turns of the second winding (Lp) beinggreater than the number of turns of the first winding (Ls), the firstend of the first winding (Ls) being connected to a mid point of a firstbranch connecting the positive voltage (Vp) to the negative voltage (Vm)and comprising a first diode (D1) and a second diode (D2) inverselymounted, the mid point of the first branch being situated between thefirst diode (D1) and the second diode (D2), the second end of the firstwinding (Ls) being connected to earth, the first end of the secondwinding (Lp) being connected to a mid point of a second branchconnecting the positive voltage (Vp) to the negative voltage (Vm), thepart of the second branch connecting its mid point to the positivevoltage (Vp) comprising, arranged in series, a first switch formingmeans (Q1) and a third diode (D3) directly mounted in relation to thepositive voltage (Vp) and together forming a unidirectional switch withdirect and inverse blocking capability, the part of the second branchconnecting its mid point to the negative voltage (Vm) comprising,arranged in series, a second switch forming means (Q2) and a fourthdiode (D4) directly mounted in relation to the negative voltage (Vm) andtogether forming a unidirectional switch with direct and inverseblocking capability, the second end of the second winding (Lp) beingconnected to the output terminal (S).
 2. Chopping converter according toclaim 1, in which a smoothing capacitor (Cs) is connected between thefirst output terminal (SP) of the converter and earth.
 3. Choppingconverter according to one of claims 1 or 2, in which, in the secondbranch connecting the positive voltage (Vp) to the negative voltage(Vm), said arrangement in series consists in arranging the first (Q1)and second (Q2) switch forming means on the side of the respectivepositive or negative voltages and arranging the third (D3) and fourth(D4) diodes on the side of the mid point of the second branch. 4.Chopping converter according to any of claims 1 to 3, in which the first(Q1) and second (Q2) switch forming means are chosen among MOStransistors, bipolar transistors and IGBT transistors or any otherswitch having a bidirectional conduction capability and a directblocking capability.
 5. Chopping converter according to any of claims 1to 4, further comprising means (11) of measuring the output voltage ofthe converter, this measuring means delivering an output signalrepresentative of the output voltage to a first input of a regulationmeans (12) in which a second input receives a set point signal, theregulation means (12) delivering a signal supplied to the input of amodulator (13) in which a first output sends a command signal (SQ1) tothe first switch forming means (Q1) and in which a second output sends acommand signal (SQ2) to the second switch forming means (Q2), theconverter being thereby configured in voltage source.
 6. Choppingconverter according to any of claims 1 to 4, further comprising means(21) of measuring the output current (is) of the converter, thismeasuring means delivering an output signal representative of the outputcurrent of the converter to a first input of a regulation means (22) inwhich a second input receives a set point signal, the regulation means(22) delivering a signal supplied to the input of a modulator (23) inwhich a first output sends a command signal (SQ1) to the first switchforming means (Q1) and in which a second output sends a command signal(SQ2) to the second switch forming means (Q2), the converter beingconfigured in current source.
 7. Electromechanical actuator controlcomprising a chopping converter according to any of claims 1 to
 6. 8.Regulating automaton comprising a chopping converter according to any ofclaims 1 to
 6. 9. Terrestrial, naval or aeronautic equipment comprisinga chopping converter according to any of claims 1 to
 6. 10. Turbineengine comprising a chopping converter according to any of claims 1 to6.
 11. Method for operating a chopping converter according to any ofclaims 1 to 6, the converter being supplied by a positive voltage (Vp)and a negative voltage (Vm) with respect to earth, the converterdelivering an output current (is) in a load (z) connected between thefirst output terminal (SP) and the second output terminal (SM), themethod comprising the following steps, for an operating cycle and topass a negative current in the load (Z): a first step during which afirst switch forming means (Q1) are open, the fourth diode (D4) isconducting, the second switch forming means (Q2) are closed and thefirst (D1), second (D2) and third (D3) diodes are blocked during a firstpart of the cycle, the converter operating in continuous mode or indiscontinuous mode, a second step, following the first step, duringwhich, the first (Q1) and second (Q2) switch forming means are open, thesecond diode (D2) is conducting and the first (D1), third (D3) andfourth (D4) diodes are blocked during a second part of the cycle, thissecond part of the cycle not ending the cycle if the converter operatesin discontinuous mode and ending the cycle if the converter operates incontinuous mode, a third step, following the second step if theconverter operates in discontinuous mode, during which the first (Q1)and second (Q2) switch forming means are open and the first (D1), second(D2), third (D3) and fourth (D4) diodes are blocked during a third partof the cycle ending at the end of the cycle.
 12. Method for operating achopping converter according to any of claims 1 to 6, supplied by apositive voltage (Vp) and a negative voltage (Vm) with respect to earth,the converter delivering an output current (is) in a load (Z) connectedbetween the first output terminal (SP) and the second output terminal(SM), the method comprising the following steps, for an operating cycleand to pass a positive current in the load (Z): a first step duringwhich a first switch forming means (Q1) are closed, the third diode (D3)is conducting, the second switch forming means (Q2) are open and thefirst (D1), second (D2) and fourth (D4) diodes are blocked during afirst part of the cycle, the converter operating in continuous mode orin discontinuous mode, a second step, following the first step, duringwhich the first diode (D1) is conducting, the first (Q1) and second (Q2)switch forming means are open and the second (D2), third (D3) and fourth(D4) diodes are blocked during a second part of the cycle, this secondpart of the cycle not ending the cycle if the converter operates indiscontinuous mode and ending the cycle if the converter operates incontinuous mode, a third step, following the second step if theconverter operates in discontinuous mode, during which the first (Q1)and second (Q2) switch forming means are open, the first (D1), second(D2), third (D3) and fourth (D4) diodes are blocked, during a third partof the cycle ending at the end of the cycle.
 13. Method for operating achopping converter according to any of claims 1 to 6, supplied by apositive voltage (Vp) and a negative voltage (Vm) with respect to earth,the converter delivering an output current (is) in a load (Z) connectedbetween the first output terminal (SP) and the second output terminal(SM), the method comprising the following steps, for an operating cycleand to pass a negative current in the load (Z), the converter operatingin continuous mode: a first step during which a first switch formingmeans (Q1) are closed, the third diode (D3) is conducting, the secondswitch forming means (Q2) are open and the first (D1) and fourth (D4)diodes are blocked, the second diode (D2) being blocked if the voltageto the first output (SP) with respect to earth is, in absolute value,sufficiently low during a first part of the cycle, a second step,following the first step, during which the first diode (D1) isconducting, the first (Q1) and second (Q2) switch forming means are openand the second (D2), third (D3) and fourth (D4) diodes are blockedduring a second part of the cycle, a third step, following the secondstep, during which the second switch forming means (Q2) are closed, thefourth diode (D4) is conducting, a first switch forming means (Q1) areopen and the first (D1), second (D2) and third (D3) diodes are blocked,during a third part of the cycle, a fourth step, following the thirdstep, during which the second diode (D2) is conducting, the first (Q1)and second (Q2) switch forming means are open and the first (D1), third(D3) and fourth (D4) diodes are blocked, during a fourth part of thecycle ending at the end of the cycle.
 14. Method for operating achopping converter according to any of claims 1 to 6, the converterbeing supplied by a positive voltage (Vp) and a negative voltage (Vm)with respect to earth, the converter delivering an output current (is)in a load (Z) connected between the first output terminal (SP) and thesecond output terminal (SM), the method comprising the following steps,for an operating cycle and to pass a positive current in the load (Z),the converter operating in continuous mode: a first step during which afirst switch forming means (Q1) are closed, the third diode (D3) isconducting, the second switch forming means (Q2) are open, the first(D1), second (D2) and fourth (D4) diodes are blocked during a first partof the cycle, a second step, following the first step, during which thefirst diode (D1) is conducting, the first (Q1) and second (Q2) switchforming means are open and the second (D2), third (D3) and fourth (D4)diodes are blocked during a second part of the cycle, a third step,following the second step, during which the second switch forming means(Q2) are closed, the fourth diode (D4) is conducting, a first switchforming means (Q1) are open, the second (D2) and third (D3) diodes areblocked, the first diode (D1) is blocked if the voltage to the firstoutput (SP) with respect to earth is, in absolute value, sufficientlylow, during a third part of the cycle, a fourth step, following thethird step, during which the second diode (D2) is conducting, the first(Q1) and second (Q2) switch forming means are open and the first (D1),third (D3) and fourth (D4) diodes are blocked, during a fourth part ofthe cycle ending at the end of the cycle.